Lee de fobest



No. 750,180. PATENTED JAN. 19, 1904. L. DE FOREST.

METHOD OF CONTROLLING SPARK PRODUCTION.

APPLIOATION FILED JUNE 17 1903.

N0 MODEL.-

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UNITED STATES Iatented anuai y I9, 1904.

LEE DE FOREST, OF NEW YORK, N. Y.

METHOD OF CONTROLLING SPARK PRODUCTION.

SPECIFICATION forming part of Letters Patent No. 750,180, dated January 19, 1904.

Application filed June 17, 1903. Serial No. 161,891. (No model.)

To aZZ whom it may concern.-

Be it known that I, LEE DE FOREST, a citizen of the United States, and a resident of the city, county, and State of New York, have invented certain new and useful Improvements in Methods of Controlling Spark Production, of which the following is a specification.

My invention relates to a new method of operating wireless telegraph transmitters whereby certain of the more serious troubles which ordinarily accompany the use of heavy currents may be reduced or eliminated.

The purpose of my invention will be set forth in the following description, and its scope will be defined in the claims terminating the same.

In the drawings accompanying herewith I have shown mechanisms illustrating preferred methods for carrying out my invention.

Figure 1 shows a mechanism for carrying out my invention employing what I have called a trigger-spark. Fig. 2 shows mechanism for carrying out my invention containing a source of ultra-violet light. Fig. 3 shows mechanism for carrying out my invention employing an X-ray tube.

In operating powerful wireless-telegraph transmitters such, for instance, as employ currents of five or six kilo watts and over-I have found that a direct make-and-break key inserted in the energizing-current has many disadvantages. The sudden fall, release, and application of the load to the dynamic generator, which is preferably employed as the source of such heavy currents, produces heavy and injurious strains, both electrical and mechanical. Independently of this the heavy current produces arcs at the contact-points, which soon consumes them. I have discovered that this may be avoided by the use of another method for producing the spark and by the use of mechanisms which are simple and reliable in their action and are not subject to rapid deterioration by use.

My method, briefly stated, consists in employing a normally inoperative spark-gap in a circuit which is constantly charged and in determining the production of the spark by the use of means which are capable of intermittently making said spark operative. Various means for making the spark-gap operative are available, a sufficient number of these being herein shown and described to make clear the principles and operation of my invention. I have found that if the spark-gap is just too wide to be broken down by the potential there applied the conductivity of the spark-gap can be suddenly increased sufliciently to allow an abrupt and satisfactory discharge, which increase in conductivity may be practically accomplished by producing an ionization of the dielectric between the terminals. This may be done in a variety of ways. It is a known fact that a spark occurs more readily and at a greater distance through a medium or dielectric which has been ionized than through the same medium when not ionized. If, therefore, the spark-balls be separated a distance too great to permit sparking between them under normal conditions and then if the dielectric between them be ionized, the resistance is thereby reduced, and sparking will occur and continue as long as this ionizing influence is continued. A transmitting apparatus may be operated by this method without using those means which cause the greatest trouble in the ordinary method of operation. The ionization of the intervening medium may be accomplished by a variety of mechanisms. A simple and practical means is shown in Fig. 1. In this I have shown an alternating-current generator G, a step-up transformer T, sparkgap S, condensers C, a radiatingantenna A, an earth or capacity connection E, and an inductance I in the antenna-circuit. These features are common in transmitters and are shown only as illustrative of a form of transmitting mechanism which may be operated by my method. My method is, however, not limited to use with this type of apparatus, but may be employed with most if not all types of wave generating or transmitting apparatus.

With the apparatus shown in Fig. 1 I have employed what I call a trigger-spark or trigger-key. This comprises a key and apparatus working under relatively small electrical stress and volume of current, but adapted to act as a trigger or means for producing a condition which will permit the action of the more powerful operating-current to thereby produce the spark which charges the radiating antenna. This trigger mechanism comprises a spark-gap operated by an auxiliary current and connected with one of the terminals of the main or operating spark-gap, so as to emit a radiation which by ionization of the medium between said sparking terminals or otherwise breaks down the resistance between them sufficiently to enable the charge therein to jump across the gap. When the effect of this auxiliary mechanism ceases, the normal condition is restored sufficiently to terminate the production of the spark. As illustrated in Fig. 1, this trigger mechanism comprises an induction-coil I), spark-gap S connected therewith, a battery B, interrupter F, and key K. This mechanism may, however, be replaced by any other suitable mechanism for the production of a spark. One terminal of the secondary of the inductioncoil is connected with one of the terminals of the auxiliary spark-gap S and also with one terminal of the main spark-gap S. The other terminal of the coil secondary is connected with the other terminal of the auxiliary sparkgap S and with a sparking terminal S, placed adjacent to and cooperating with that ore of the terminals of the main spark-gap S to which the other terminal of the coil is connected to form therewith a small spark-gap. I have shown this terminal S as placed at right angles to the direction of the main sparkgap, although it may be placed in various other positionsas, for instance, in line with the main spark gap and between its terminals. It is sufficient that the trigger-spark occur in the vicinity of the main spark-gap. The connection of the terminal S with the induction-coil or other source of high potential may be omitted, in which case the singlewire connection with one of the terminals S is retained. In this case when the triggerkey is depressed a brush-discharge is produced from this terminal S, which ionizes the insulating dielectric and allows the main oscillating discharge to take place. If ultra-yiolet rays be thrown upon the spark-gap, the same result may be obtained. This means is illustrated in Fig. 2, which in the main transmitting mechanism is the same as in Fig. 1. In this figure an are using preferably iron terminals J and a reflector L, focused upon the spark-gap, is shown as a source of ultraviolet rays. The spark gap is normally screened from these rays, as by means of an opaque shutter N, which is movably controlled by a key K, so as to permit the rays to fall upon the dielectric of the spark-gap when desired. I find that as a source of ultra-violet light an electric are between iron electrodes in atmosphere of dry hydrogen is especially eflicient. X-ray radiation possesses the same property of increasing the conductivity of the spark-gap, probably due to the presence of the so-called Blondlot rays. A method of using this is shown in Fig. 3, in which P represents an X-ray tube, B the battery for operating the same, K a key for controlling the application of the current to the tube, and D the transformer in the X-ray system. It will be seen that the keys for operating these devices are all either in a circuit carrying but a small amount of current and at a low potential or entirely out of any circuit. As a consequence all troubles due to the use of a key for making and breaking large currents are eliminated.

The discharges produced by my method commence promptly with the application of the trigger-spark or other radiating or ionizing influence and cease abruptly with its cessation, and is therefore exactly controlled in its action by the trigger-key. So closely is this main spark governed by the auxiliary influence that I have found its frequency closely governed by that of the trigger-spark, when such is employed, so that although the generator Gr may be a high-frequency alternatingcurrent generator, yet if the interrupter of the trigger induction-coil be of the ordinary hammer type and of a low frequency the frequency of the main spark is generally that of the trigger-spark.

By my method I am enabled to not only exactly control the discharge of a powerful transmitter by a simple Morse key operating in a small current, but to also easily and exactly control the spark frequency of the transmitter independently of the frequency of the generator and of any fluctuations thereof, and thus to eflectively avail myself of the principle known in the art as mechanical tuning with an accuracy diflicult, if not impossible, by other means where an alternating current is employed of varying or fluctuating frequency.

It is evident to one familiar with the art that the principle of employing an auxiliary trigger or pilot mechanism or influence to render a normally inoperative spark-gap operative may be applied in a great variety of ways. I do not, therefore, wish to be understood as limiting myself to the use of the exact means herein shown and described, but to be understood as claiming all variations which fall within the terms of the accompanying claims when broadly interpreted.

What I claim, and desire to secure by Letters Patent, is

1. In spark telegraphy, the method of precipitating sparks between normally inoperative sparking terminals which consists in increasing at will the condition of ionization of the medium between the sparking terminals.

2. In spark telegraphy, the method of precipitating sparks between normally inoperative sparking terminals which consists in increasing at will the specific conductivity of the medium between said. terminals.

3. In spark telegraphy, the method of determining the intermittent production of the signal-sparks which consists in intermittently subjecting the medium between the sparking terminals to an ionizing influence correspond ing in time and duration with the time and duration of the sparks desired.

4. In spark telegraphy, the method of determining the spark production which consists in separating the terminals by a distance norreally too great to permit sparking, and in then reducing the resistance of the medium between said terminals at times corresponding with the times of the sparks desired.

5. In spark telegraphy, the method of producing the signal-waves which consists in employing a normally inoperative spark-gap and in intermittently subjecting the same in accordance with the elements of a signal-code, to an influence adapted to lower the insulating capacity of the media between the sparking terminals.

6. In spark telegraphy, the method of determining the time of spark discharge, which consists in intermittently subjecting a normally inoperative spark-gap to electrical radiations from an independent source.

7. In spark telegraphy, the method of determining the production of the spark discharge which consists in employing a normally inoperative spark-gap and in intermittently making the same operative by the production of an auxiliary or precipitating spark adjacent thereto.

8. In spark telegraphy, the method of producing the spark discharge in a normally inoperative spark-gap which consists in subjecting the media between the sparking terminals at will to the influence of an independent force adapted to break down its resistance.

In testimony whereof I have hereunto affixed my signature, this 15th day of June, 

